Liquid spring



A2,sw5,262

Feb. 16, 1960 R. F. zUMwALT LIQUID SPRING 2 Sheets-Sheet 1 Filed Sept. 5, 195

INVENTOR. HUBERT lg' ZUMWALT Afro/mfr l/v Feb. 16, 1960 LIQUID SPRING 2 4Sheets-Sheet 2 File@ Sept. 5, 1956 wnznom z. momo...

l/ l l ll l STROKE IN INCHS lFIG. 4.

STROKE IN INCHES 1NVENTOR. L /6' fROBERT/z' ZUMIYALT On I- :orx 1pl eti;m o f the Ninward stroke' on the mainpiston;` vthe expanding liquid Ih'e primary andsecondary chambers forces this piston outwardly, aided by: the .preSz aureof the auxiliary' liquid s'pring-on-.the' floating piston m the secondary chamberrluntil the :main "piston has moved Ifar enough on its Ireturn stroke forithefpoppet valve' to again close off thegprimary chamber from the secondary`chamber. Then the return' stroke continues'at chambers 'to ,such a l.postiontluit the second set of'bl'eed.

in' Fig."1 by' the'rod or' plunger 44' of a" conventional @faster ratevuntil -the pressure in the. primary. chamber phiahem reduced to zero. -gThen'thezr'nain p istomin' It; returnl strokewill .have moved far enough for the poppet val-ve to again open thev primary-.chamber to the secondarycharnber vso thatzthe pressure of the liquidin the secondary-chamber will complete the return move'- ment of themain piston toits starting position.'

l Referring now to the drawings. byI numerals. of reference,j 10 denotes the housing of the main liquid spring. Thishousing is formedwith a primary chamber l1 and with .asecondary chamber 12. A partition wall 14 formed in the housing separates the two chambers ll'and 12; but these Atwochambers are connectablewith one another through a bore or port k15 that .extends throughthe partition wall' 14. The outerendof thechamber 11 isvfcluosedv by a plug 16 that is brazed or welded .around iajgeriphervto the Aside wall 17. of the chamber 11. The plug 1 6 isformedwithacentrally disposed bore which'constitutes a guide cylinder 20. A piston 21'is mounted. to reciprocate in theguide-'cylinder'20. This piston' carriesa conventional nylon or votherseal-ZZ toprevent leakage of liquid from the chamber 1.1' outwardly along the piston.v The piston has. at one end-a' piston'rod 23 which projects outwardly of :the chamber 11 through an opening in the closure plugv.16. A nut 24, which threads on the closure plug,'and aseal 25,1 which is heldin positionl by the ynut 24, serve tolirnit outward movement of the piston-21. l

Withinthe Vchamber 11 the main piston 21 is formed with a portion 27 of'reduced` diameter which extends inwardly beyond the p iston head 21; and this portion 2 7 is lfurther reducedin diameter as denoted at-`28=toforma shoulder 29. v f

ls ieatted on and `around the reduced diameter portion 28 ofthe main piston 21 and fixed thereto, as byfshrinki ing it on the reduced diameter portion 28, is apoppet sleeve valve 30.- This valve is formed with-'two sets of anially spaced bleed slots. One, set of these slots cornprises two axially-extending diametrally-opposed-recesses 52(F.ig. 2)'` which extend from the inner end 4"of the valve forwardly for a. portion o'f its length. AThe other 'j valve will close off the chamber 11 from thechamber'12 and prevent flow of liquid through the bore 15.-

.Mountedto reciprocate in a-cylindrical guide portion 40 vformedjin the secondary chamber 12 is a-'oating piston.41. -This piston carries in a peripheralrecess anA O-ring or other suitable seal 42 which'engagesthe walls of the cylindrical guide surface 404 to ,prevent leakag`e of .liquid from the chamber 12 outwardly along'wtheip i'sf"l The `rpisfon' 41 germany vhun in -fhe posing-sii sagen 75 ton 41.

liquid spring 45. This spring comprises a container or housing 46 which is provided with a chamber 47 that is formed at one end with vva cylindrical guide bore 48 and that is closed at its other end by a plug 49. The plug 49 is brazed or otherwise fastened in the housing. A piston 5i), with which the piston rod 44 is integral, reciprocates in the cylindrical guide portion 48. This 'piston carries a nylon or other suitable seal 51, to prevent leakage of liquid from the chamber 47 outwardly along the pistonfS.v The. forward end of the' piston 4rod 44 abuts against the rear'face of the floating'piston 41.

The liquid spring is secured to the housing 10 b y an adapternut int'owwhich' the reduced diameter'fxeck portion 56 of the .housing is threaded, yand which threads onto a reduced diameter neck portion 58 of the housing 10. A combined seal and stop 57 is held in place in the forward end of guide bore 48 by nut 55. The partm57 cts asa 4forward rli'mitstop 'for piston 5.0. -1

.The chambers 11, .12 and '.47 .are-adapted-to-be filled with a compressible liquid such as a silicone liquidi.' This liquid may'be supplied tothe chamber 11 from a-pump not shown through the'piping .60; a. valve V6 1, and the piping 62. The valve 61 is -simplya conventional shut-' off valve to shut olf the' supply line from the pumpv when thefdesired -preload pressure has been obtain'edin 'the' chamber 11. The 'pipe 62 communicateswi'th" the chain#v ber ll'through the duct or port 63. in one side wall of the housing -10.-f The ipiping 62 is" secured in position'by' means .of a conventional'nipples which contains y'a packingggland 64..f a'

4 Similarly' liquid under pressurel is'l supplied? tol/the' chamber 12 fro'mfa pump (not shownl'through piping 70, a conventional 'shutoly valve 71,-v and' pipingA 72.# Piping 72 communicates ywith the chamber A:12' through a port orv duct 73;?and the piping 72 is-held inposition by. apacking gland 74 vand a nipp1e 75 `which threads into the housing 10.

"11,1- Thevolume 'of liquid lin thechamber 11 is controlled by.;an` adjustment` nut whichl threads 'on aI lateralprotrusion or lboss 81 which -extends laterally of vthe housing 10. 'This .nu't engages a shoulder 82 on theshank Y or rod 83 of a piston 84 that is adjustable by' means-ofthenut inthe cylindrical'guide bore' 85 of--the extensin 81 and that is freely movable therein. A nylon or'other u"suitable sealv 86 is mounted -onthefpiston 84 to vprevent leakage. of liquid from 'the chamber '1'1" along'lthe pistoni 84. .1. `Guide bore A8 5 communicates-with 'chamber V--lls and Vinf-effect is par-'tofthat-chamber.;- 'Ihe'fguidebore j85, like the rest of 'the' chamber 11,1 isriilledLtdthe vitent allowed by!-theadjustedposition of piston 84 .v vitlr' the compressible liquid. 15. 'f y wr c Ai w 'ln similar manner the adjustment' of thef volume of the liquid 'iin' the chamber'12 canbe controlle'dby'an" adjustment nut 90 whichv engages -the shoulder ,on' a piston 94 similar to the piston 84. This nut'threads'onl'a lateral cylindrical extension' 91 of 'housing VV10;` and-the piston 94 reciprocates'ina cylindrical bore "95.formed inthis extensionand communicating with' the' chamber 12.' The bore. 95,` like Vthe rest of chamberf112,.is='lle'd tothe extent allowed bvthe adjusted .positionwof piston 94 with the compressible'liquid'. .11` .1 f The conventional liquid spring 45xislle'din conven tional manner'wi'th'the compressible liquid. rl

The operation of, thedevice will lbeunderstood .from the preceding description, but maybe briey summedllp here.l .v. vWhen an outsidefo'r'ce is applied to the piston'rod 224v the main piston 22 is moved Ainwardly in the housing 10,

compressing the liquid in the primary and secondary chambers slightly through `operationof ,the piston g21 whose area is greater than the area ofjthepistonf21 plus ber 12 'there is at this momenteel sudden 'transfer 'or lig'id `chamber 11 will haveidropped .vsubstantiallytofzera From .then on, iixi the return stroke, ,the priricipalpressure Y in pressure ci the k1i quizi1,jin these'. chambers :i

Vmary chamber .is Adisplaced the -mi piston pressure in the secondary chamber 12 Arises :a l rate dueto the zfact that anyerise intpressure the liquid less than Ithe vpressure built up by that assembly; hen rf the primaryV and secondary chambersuare sealedof from 4S l"te tke mest ef the pressure., Wheu *the pisteii 21 hasmdvetl far enough inwardly/, e'thetigh, for the; vrpp'et Y valve -seeton 35 to enter ifthe v bore 15, jthen 'the primary chamber `l11 ris `shut Y'o from the secondary haxber 112. As the `puppet 'valve moves inwardly inthe ibore 15 .it l compresses the liquid inthe chamber1'2 "somewhat, but the compression of this liquidis 'again absorbed by the auxiliaryspr'ing 45. It is 'the liquid 'in the primary chamber 11 lwhich is most compressed fwhe'n the bambers 11 and .1 2 are shut oi 'from one another. The liquid iu-YU lthe chamber 11'i's 'compressed 'at 'a 'very high Arate resulting in a rapid .increase 'in 'the I,pressure 'in tha't chamber. Continued inward movement of the main pistoia 21 Jevetil s it'ihri's'fvncl endfheeee #fthe-portee@ wy l p 30e-2 8 isithe' piston a'refav` `'acting ,111k the prima lhejtetal fierce' 'developed "byl the main piston is gf the idf' forceA developed res'v ting fijcmjthe'pressuregrse in Vthe primary cheniberjis'jg'reat; c therefore, as compared 'Withthje force developed in the seeondary'chamber. The -axru'nu1-1tof .ferte idevelopedgby the :systemand the individualjchjamberfpiston 'combinatien is epnteeuedgby thedesign ef the device itself;

p ciint,Y b fwhe'r'e' the'puppet valve 30 has npvedjrar enough fort'he xbleed's lo'tsf to connect the primaychab'r 1 '1 ajg'a'i'n wthjthe secondarychajmberlz, At 'this ,peint there yis 'a sudden 'pressure dre denoted 'by the :Iie 103,; to a position 'such that ihe secondary bleed vslots 33 in '1 5 to Ythe point c. i j l the puppet valve again permit communication of 'the 'two In ith-e Jretu'r'n hjalff or "the operating cyclethe exjaiding `chambers 11 and 12. rSince the pressure in the 'primary liquid in the chambers 1'1, 1'2 il 147, orc I Qn `chetimbei- "11 exceeds the pressure 'in the secondary c ha'm- 21 "to j t'heleft until vthe 'fr'gorti :1.35ct thepcppet s agai "seals 'off the port 15. "'Untilgtlisbccurs gfhe; frointhe 'pr'marycharjnber 1'11 to 'thefsecortd'arv chamber 20 return is at thes'p ng rate evielqped lzwhich causes a sudden. pressure :drqpin'the primary of the .ccmbinea chamber 'and a pressure rise 'in 'the secondary chamber. seriesv v'vith 1the' floattngvpst'o' The chamberfpressures are.'therebyr e c1'1'1a`lz e`t i 30 hasagan sedledfofffthegprlr' Upon V competi'on of thewerkin'gsjtr'oke o'f jthejmin secondaryche'rbei,"which occrjs liston 21 and relief-fof `the j fe'rce",en thepbistenliedjes; '25Y ata -in the diagramme ra'tec lead die h the liquid inthe threefchaniber's113 121 and 47gexpanjds, V'tc fthe 'fact'.tht .tti 'iiquid .in the 'primaj the piston 50 andjpistcmtod'44v causingftetur'njncvetent 'e ofithe'oating 'pistn 41,'and1thejexpans` n ofthe .liquid e in .the `chambers 1 1 and'12ac :aus'ihfg,retul the piston 421. This retur movement Y 'rate fhtfil the ,pqppe't'val-vefin lifts"finer/ein'e1'1`t'lvl/it;y ,t piston ZLag'ain closes elf the port I Then `the ,;r etl1 r1 i.- v mvementof the pistn'f21-"is 'caused ridiarily. "theeexpansion of the .liquilhn -the fprimayfchamh When fthepoppet valve 30 has .moved far ,.enou'gh," h oiv- 'i 7s' eet-teiijiv chamber, whiehlet mestcamenlye isgqette .Het te the peintvgtieregthe .ist. set;ef g u`1eea stets 32 again connects fthe primary .chamber with the .Secund will be on the exposed `surfaces of thepoppetevalve 40 ary chamber.. Thisbccurs atthe pointj in.thetdizcgx'ram lhen .the v total Aareaof the main pistonjistexposed'tothe further reduced pressurefvduefto venting the` assembly 30e-'28; and .the liquid .will ow fr ornchamber 12 into chamber 11 until Ypiston 21 has `retliititedltd initial position. v e 'r j t .Oneway Iin which .the .springlof Eig. .lrmay perate is illustrated diagrammatically in Eig. '3e .YInth v 1 represents the normal .starting point of the s munieatien betweenrhe chambers 11 .and 12e This is represented 'bythe-liueIUL A'tg 'he p'oppetjvlve `section 3s enter'sthetle'r the 'primary chamber ifrc'jme' 'secegtia`AI After "the primary and secondary 'charrib 'hvefbeeh-l` sealed Aoff from one another, .the pressure-fin the `iii mary E g chamber rises very ,rapidly, 'this',riseln'jpressure' denoted in the diagram -of 3 f .by vthe line-P10 pressure of the liquid in 'the primary 'chambery atta much more .rapid rate ythan inthesecondary ch bersince the liquid in thepr'may c'harr'lbet Wil'l bec my pressed,V after sealing off of thetvvo chambers fre` ne. anotheig'by -the ,amount by yWhich the liquidjiiit'he pri- 1;"The Through adjsft'mentlftlle*pistons` Y U lesser-'65 fnrimry and-secndary, ha bers, of liquid.

in't'hcsechatnbefrs canibe'centrelled'i Thesepistens conf j in -tihat chamber is reilected .by movemeutuffgthefloating trol'theindependeht .springjrateofeach chamber aswellV i pistou 4i vagainst the auxiliary {spring-45. The SprigS f will be selected, of course,` so that the pressure, lvvh'icll it exerts. contra to valve-pistony assembly Sil-:28 will beY ton a'area.

f'splingv can be changed by installing diierent springs', o r "in-"the case shown, therateof the auxiliary spring 'can be changed 4by changing the liquid in the auxiliary .spring` 'j I'nFig. 3 the'full lines X denote th'eiforce-.stroke curve under 'averagel adjustmentof vthe spring. "'With .the minimiii'volume of'liquid'in the liquid chambers 11.5and 1.2', .lllf I r'lXmumfspring 'ra te"car'1 'beobtainedvv 'The forcelstroke curve for this -co'ndit'ion'is 'shown in .the'd'a'sh linesfatY. With themaximumvolume of liquid in the chambers 1-1' and,f12,'theminiir`1um .s 'p`ring' rate is obtain-n A further adjustment possible andprobab1yidne: which l" will' .permit grfearevariatn and distortion fthe force- ?trQke diagram cari befmfd by @hanging thepppe't valve itse1f. Poppet valves` with ditferentlengthsand positions' of bleed'slotscan be "provided, thereby to' control" the pointiat v vvhichjthe primary and, secondary 'chambers' are vented tofeacho'ther and sealed off from each other., A 'The force-stroke diagrams of Figs. 4 and' 5 illustrate variations inthe spring rat e obtainable through' altering fthefbleeds in theploppet'valv@ t' t The Vforce-stroke diagram of Fig. 4 shows the curve ptducedwhenhthe" primary .Chamber and .ssondary chamber are sealed from each other Vat the start of the operating'cycle. In this ca se,"the pressure rise in the device isv quite rapid until point a i'sattained where the bleed slots'allow communication of chambers 11 and 1 2. Then 4thereis anextremely rapid fall in pressure for afshort portion of Athelworkin'gstroke of main piston 21 witha gradual rise inpressure againuntil the working stroke of'thefpiston'is completed at pointe. `Onthe Vreturn strt'glte ofthe "piston 'a corresponding gradual `fall in lpressure, due tbferrpansion of the liquid in i1owcom4 municating :ch'ambersjll and 12- takes placeV until chambe'rs' 11i-and 12 are "again sealed'o from one another by poppetvalve 3D. The piston 21. will then have returned to initial: position.V Further variations are obtainable through alteringinitial loperating pressures in each chamber.V A still further variation is obtainable through the volume adjustment of the amount of liquid in eithery or bothehmbersj- The forcestroke'diagram 'o fV Fig. v Srepresents the curve obtained when thewchambers' aresealed ott` from each other for'only a minor portion of the total operating stroke.` The suddenirise to the peak of the curve is again produced principally by the'rapidchange of pressure rise due-'toisealing'o't the primary chamber from'the second# Y chamber andthe resultant compression'ofthe liquid to a higher degreein the primary chamber.

f' 'The same letters are used in the diagrams of Figs. 4 and 5 as` inFigB t denote thesarne points at which 'different steps'fin the operationof the spring occur., Whilethe invention hasbeen described in Vconnection with "a specific embodiment thereof and particular usesV therefor, it willbe understood that it is capable of further modification and use',v and this application is intended to cover any variations, uses, or adaptations ofthe invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains 'and as may fall within the scope ofthe' invention or Vthe limits of the appended claims.

" laftedthereby' to close oiffsaid'port during inwardmovement of said pistn, and a pair of additional means each in uid communication directly with only one of lsaid chambers respectively for separately varying the pressure of the .liquidfinlthe two chambers,v said piston being responsive'to Aexpansion of Isaid, liquid vto be r turned 3. A; liquid spring comprising'` ahousing 'having 'twol chambers'` 'thereina'nd a normally open port 'cjonfnect'ing said chambers', said chambers 'beingfilled with acorn? pressible liquid, "'a piston movable'. inwardly of one of said chambers upon Iapplication of an outside force t hereto,' valve vmeans connected to Ysaid piston* to be operated therebyto close off said port during inward movement of said piston, and additional means. for separately varying the volume of eachofthe two chambers; 4. Aliquil spring'according to claim Shaving means valso.forseparately varying the pressure of the liquid in ea'ch of thetwocharnbers. 1

5. 'A liquid spring comprising a housing having two chambers therein and a port connecting said chambers, said chambers being filled witha compressible liquid, "a main piston movable inwardly into one of said chambers upon application of an'outside force thereto, valve means having a movable sealing surface adapted to v engage said port and positively connected to said piston to be operated thereby in both directions and movable at ally times therewith' to control the opening and closing of vsaid port, said main piston being operative on inward movement when said port is open to increase the pressure on both ofsaid chambers, a floating piston reciprocable in the other chamber, 'and liquid spring means constantly urging said oating piston toward said main piston.

6. A liquid spring comprising a housing having two chambers `therein and a port connecting said chambers, said chambers being lled with a compressible liquid, a

' main piston 'axially aligned with said port and reciproc- Having thus:4 described my invention,what l claim is; Y

.1. A liquid spring comprising a plurality of rigid chambersiilledi with a compressible liquid and freely communieating with each other under zero-load conditions,an ini perforate piston movable inwardly of one of said vchambers upon application of an outside 'force thereto, and means movable` vby said piston within each of said chambers' .iorsuccessively closing ott said chambers Vfronrcun able in 'one of said chambers, a sleeve'valve carried by said 'main piston and .slidable in said port and having bleed slots along part of its length to permit communicationjbetwee'n said chambers and being formedalong auf other Vpart of its length to close said port, a floating piston reciprocable in the other chamber, and spring means constantly urging said oating'piston toward said main piston, the effective 'area of said floating piston being greater than the area of said port.

7. A liquid spring Yaccording to claim 6in which the eective ,areaof said oating v.piston s greater than the elective area of said main piston and of said port combined.

8. A liquid spring according to claim .6 having separate means for' supplying liquid to said two chambers, respectively.

9. `A liquid springaccording to claim 6 having sepa rate means for adjusting the volumes ofl said two cham# bers, respectively. v

`10.'A liquid spring comprising a housing having' two chambers therein and va port connecting said chambers, said chambers being lled with a compressible liquid, amain piston reciprocable in one of said chambers and movable inwardly of said one chamber upon application of an outside force to said pistonto compress theA liquid in said one chamber, a sleeve valve secured to said main .piston to reciprocate therewith and through said port,

' sure in communication With saidchamber; and means to a volume-controlling piston slidably adjustable in each `of said cylinders, means for separately adjusting each of said volume-controlling pistons to control the volume of its respective chamber, and means for separately supplying liquid to the two chambers. 7

11. A liquid spring comprising in combination: an inexible container having a chamber; a compressible` liquid v'ammassi s wardly of one of saidchambers, upon application of an outside force thereto, to compress said liquid, and movable in the opposite direction by expansion of said liquid filling said chamber; a'rst piston reciprocable.V in said w container and movable in one direction in said container,

upon applicationof v an-outside force to said piston, to x compress said liquid, and movable in the opposite direccontainer and movable in one direction in said container,

upon application of an outside force tosaid pattern, toV

compress said liquid, and movable( inthe opposite direction by expansion of said vliquid upon release of said Aforce; a second piston carried by said container and adapted to be selectively positioned for adjusting the volume of said chamber;a source f liquid undenprescontrol said communication -to vselectively alter th quantity of liquid in said chamber. Y

a rst piston reciprocable, insaid .1c tainer fand moyable able in the Vopposite directionqbyexpansion'of said liquid` Y upon release of-said force'favalve opera'tel,byvv saidirst "piston to closeoff and vtofreopenV said uidxintrcomf' v pression of saidliquid; and rigid means carried by said containerjfor unyieldably reacting'on said second piston I f* afterapredetermined amount of compression of saidY j munication/during theV inwardf movement fioffs-'aid Prst 1' 'f tively altering the quantity of saidV Vliquid in said chambers.

' piston; a second piston carried by saids'containenand.Av v adapted to be selectively positioned 'jfor adjustingthe t' volume of one of said chambers; andseparate 'means in uid communication with one of said chambers for selec- 40V 13. A liquid spring comprising: an inexible container i having a pair of chambers vin iluid communication with each other; a compressible liquid filling said chambers; a

upon releaseof said force; a valve operated by saidrrst f piston toV close oiand to reopen said iluid4 intercom-` munication during the inward movement of said'rst pis-v ton;ja second and a third piston carried byfsaid container vand each adapted tobe individually selectively positioned for adjusting the volume of eachl of said chambers, re-

spectively; and separateY means in iluid communication with one of said chambers for selectively altering the quantity of said liquid in saidvchambers.

14. A liquid spring comprising in combination: an inilexible container having a chamber; a compressible liquid fillingsaid chamber; a first piston reciprocable in said tion by expansionof said liquid upon release of said force; a second larger piston carried by said container andY movable by said liquid during the compression thereof in a direction uidly away from said chamber; resilient means carried by said containerrfor yieldably reacting on said 'second piston Vwith a force suflcient to vpermit comlteferencesfcitedinjli me f this Patem UNITED' sTATEsgPATENrs .11,505,036 Y 112,566,736; Levy c r` :sepa 4, 195.1l 'Y 2,723,847 `Hogan .Nv. 15, j1955 2,729,441.01` Wales' Jan. 3,`j.1956 2,743,741. ford hawaii -;s ;May`1,1956- 2,773,517' Hooperet '.'Deca 11, 1956`y j 2,793,031 Hartel ..-May Z1, 1957 v. FOREIGN PATENTS 563,913 France Oct. `6, 1923 615,549

Great Britain Ian. 7, '1949 

